1. IMMUNITY

2. What is Immunity?
Ability of the body to protect itself from viruses, bacteria, and other disease causing agents
The word immunity comes from the Latin word immunis meaning exempt

3. IMMUNE SYSTEM SPECIFIC response to foreign substances
Substances that evoke the response are called ANTIGENS
Immune response produces proteins that are specific to the antigen, these are ANTIBODIES
Specific white blood cells called LYMPHOCYTES are produced

4. Types of Acquired Immunity
Naturally acquired immunity
Artificially acquired immunity

5. Naturally acquired immunity
ACTIVE – exposure to antigen naturally in the course of daily life
This is the type of immunity from having a disease
PASSIVE – maternal antibodies transferred via the placenta or mother’s milk
Temporary immunity for the newborn

6. Artificially acquired immunity
ACTIVE – vaccination
Receive antigen via injection of vaccine
Produce antibodies against the injected antigen
PASSIVE – preformed antibodies
Receive preformed antibodies from immune person or animal
Antiserum
Temporary protection

7. Duality of Immune System
Humoral immunity
Production of antibodies
B cell activation
Active against bacteria, toxins, and viruses that are circulating in body fluids
Cell-mediated immunity
Activation of T cells
Active bacteria and viruses that are inside host cells

8. What are Antigens? Things that are foreign to our body
Usually proteins or large polysaccharides
Antigenic determinants are often parts of the invading microbe
Antibodies react with specific regions of the antigen called EPITOPES

9. Antigenic determinants

10. What are Antibodies? Antibodies are proteins
React with only ONE specific antigen
Neutralize or destroy the antigen
Each antibody has specific antigen binding sites

11. Antibody structure Consists of 4 chains 2 light and 2 heavy chains
Variable regions of antibody bind specific antigen

12. Antibody structure

13. Antibody variable regions (antigen binding sites)

14. Classes of Antibodies (Immunoglobulins)
IgG
IgM
IgA
IgD
IgE

15. IgG Single unit monomer antibody
80% of all antibodies are of this class
Crosses the placental barrier to protect fetus
Protects against CIRCULATING bacteria, viruses, and toxins

16. IgM 5 monomer antibody 5-10% of antibody in serum
First class of antibodies formed to antigen
Reacts with human ABO blood groups
Clumps the antigen

17. IgA 2 unit monomer antibody 10-15% of antibodies in serum
Abundant in mucous membranes, tears, saliva, and breast milk
Prevents pathogen attachment to mucosal surfaces

18. IgD Single unit monomer antibody 0.2% of serum antibody
Found in blood and lymph
Antigen receptor on B cells

19. IgE Single unit monomer antibody 0.002% of antibodies in serum
Binds to mast cells and basophils
Allergic reactions

21. B cells Develop in the bone marrow Migrate to lymph nodes and spleen
Recognize antigen by cell surface receptors
Activated B cells divide to form plasma cells which secrete antibody

22. Clonal Selection B cell is sensitized by specific antigen
Divides to form many more identical cells (clones)
The clones differentiate into plasma cells that secrete antibody formed against the antigen
Some cells become memory cells to provide protection for years to come

23. Clonal Selection

24. Results of Antigen-Antibody Binding
1. Agglutination
2. Opsonization
3. Neutralization
4. Complement activation
5. Inflammation

25. Results of Antigen-Antibody Binding

26. Monoclonal Antibody Production

27. Uses of Monoclonal Antibodies
Diagnostic kits
Pregnancy testing
Suppression of tissue rejection in transplants
Disease treatment

28. Primary and Secondary Immune Response
Primary response to antigen is by IgM antibodies
IgG antibody production begins several days later
Second exposure to antigen results in IgG production immediately and in large quantities
Anamnestic (memory) response

30. Memory response

31. Cell-mediated Immunity
Based on the activity of T cells
T cells are a class of lymphocytes that are produced in the bone marrow but mature in the thymus gland
Distributed in the various lymphatic organs
Effective against intracellular antigens

32. What are Cytokines and Interleukins?
Cytokines are the chemical messengers of the immune system
Interleukins are the cytokines that serve as communicators between white blood cells
There are now at least 26 different interleukins (IL) many of which have important functions in the immune system

33. T cells T cells are the key cellular component of immunity
There are 4 main types of T cells
T Helper cells*
Cytotoxic T cells*
Delayed hypersensitivity T cells
Suppressor T cells

34. CD – no not compact discs (Cluster of differentiation)
T cells carry surface receptors called CD’s that are used to differentiate between the various types of T cells
T helper cells are classified as CD4 cells by their receptor
Cytotoxic T cells are CD8 cells

35. T Helper cells
Key cell that activates cell-mediated immunity and links humoral (antibody) immunity to cell-mediated immunity
The T helper cell is attacked and destroyed by the AIDS virus leading to immune system failure

36. T - helper cells and HIV Time course

37. Helper cell activation
Antigen is presented to the helper cell by another cell called an APC cell
APC cell and T helper cell bind
APC cell secretes IL-1, T helper cell is now activated!
IL-1 simulates the T helper cell to secrete IL-2
IL-2 secretion stimulates the activated T(H) cell to form clones of itself and also to stimulate other cells such as B cells to make antibody, and T(C) to attack infected cells

38. T helper cell activation

40. Cytotoxic T cells
Once activated by the T(H) cell the T(C) seek out and destroy infected cells in the body
The T(C) bind with infected cells and release PERFORIN that causes the infected cells to burst (lyse)

41. Cytotoxic T cell activity

42. How the Cytotoxic T cells works

43. T cell/B cell interaction

44. T cell/B cell interaction

45. Immune system summary

46. Summary of cell-mediated immunity
APC’s stimulate the T(H) cell
The T(H) cell is central to both humoral and cell-mediated immunity
T(H) cells stimulate B cells to make antibody and cytotoxic T cells to destroy infected cells
Without T(H) both aspects of immunity will fail and so will you!